In various services of a mobile network at present, a video service occupies a large part of network traffic. However, a stalling phenomenon in video play severely affects user experience of a mobile video service. With introduction of new video services, such as virtual reality, the video service requires higher bandwidth and a lower delay.
In LTE/LTE-A (Long Term Evolution/Long Term Evolution Advanced), 1 ms is used as a unit (that is, 1 transmission time interval (TTI)=1 ms) to allocate a physical resource block (PRB) to a terminal (UE). There is a round trip time of 8 ms from a time at which a base station (eNB) sends a packet to a time at which the base station receives, from the UE, a feedback indicating correct receiving.
In order to reduce a round trip delay of packet transmission, a shorter TTI such as a 0.5-ms TTI or a 1-symbol-TTI is introduced. The 1-symbol TTI is used as an example. A round trip delay of transmission of one packet is eight symbols, that is, a delay less than 1 ms. With introduction of the shorter TTI, the transmission delay can be reduced, so as to meet a low-delay requirement of the video service.
The video service desires a low delay, and further desires high bandwidth due to a relatively large quantity of transmitted packets. In a scenario in which new UE supporting a 1-symbol TTI coexists with legacy UE, when the legacy UE occupies a relatively large quantity of frequency domain resources in 1 ms, if a low-delay video service bursts in this 1 ms, a relatively small quantity of time-frequency resources can be used by the new UE. This causes a delay increase.
During downlink (DL) transmission, to meet a high-bandwidth low-delay condition of the low-delay video service, a method is described as follows: A low-delay service preempts frequency domain resources on some symbols of the legacy UE, and when the low-delay service bursts in 1 ms, the base station preempts a resource element (RE) of the legacy UE, and transmits data of the low-delay service on the RE used by the legacy UE.
An advantage of the method is that the high-bandwidth low-delay requirement of the low-delay service can be met. However, in the method, incorrect receiving of the legacy UE is caused because data on some symbols of the legacy UE is not data needed by the legacy UE, and a combination gain is reduced when hybrid automatic repeat request (HARQ) combination is performed. In addition, after the legacy UE incorrectly receives data and gives the base station feedback indicating the incorrect receiving, the base station retransmits the data after 8 subframes, that is, a retransmission delay is relatively high and reaches a length of 8 subframes.
Therefore, when the new UE supporting the shorter TTI such as the 1-symbol TTI coexists with the legacy UE, after the base station preempts an RE of the legacy UE for the new UE, how to ensure receiving performance of the legacy UE is a technical problem to be resolved.